Currently, there are various kinds of studs, nuts, and spanners with different sizes. To be carried out easily and conveniently, sleeves of different sizes for suiting a D head spanner are developed.
In one prior art, each sleeve formed with two annular recesses. A nose is formed between the two annular recesses. An annular color strip is formed on the nose. The strip is protected by a protection film or a metal ink.
Furthermore, in another prior art, a periphery of a sleeve is formed with a slide stop recess and then a convex texture is formed by rolling process as an indication. A color layer is coated upon a surface of the indication. Then the indication is ground and electroplated.
In above mentioned methods, a color layer is coated upon the sleeve. Then the color layer is coated with a protection film or is electroplated. Normally, the surface of the sleeve is difficult to be cracked or is affected by wetness so that the color strip is wet or the protecting film is destroyed, or the electroplated layer is rusted so that the indications are lose of function. Thereby the above mentioned prior art is not a permanent way for retaining the indications on the sleeve.
Thereby there is an eager demand for a novel way which can improve the prior art defects so that the indication can be retained on the sleeve permanently without being affected by wetness, cracking or collision.